Pacific Ocean Circulation — Hid AKA 
205 
TABLE 4 
Computation of Theoretical Surface Velocity of the Kuroshio across the 33° N Parallel 
X = 
Distance from 
west boundary (km.) = 
0 .0025 .0050 .0075 .0100 .0125 .0150 .0175 .0200 
0 25 50 75 100 125 150 175 200 
.0225 .0250 .0275 
225 250 275 
* = 
0 
612 
815 
735 
546 
352 
195 
95 
44 
28 
31 
41 
X 10 10 cm 2 /sec 
57 
Ax/z/Ax = 
0 122.4 163.0 157.0 109.2 
70.4 
39.0 
19-0 
8.8 
5.6 
6.2 
8.2 
X 10 4 cm/sec 
d7 
Computed /For D z = 50 m. 
0 
245 
326 
314 
218 
141 
78 
38 
10 
11 
12 
16 
Velocity ; For D z = 75 m. 
0 
163 
217 
207 
146 
94 
52 
25 
12 
7 
8 
11 
(cm/sec) IFor D z = 100 m. 
0 
122 
163 
157 
109 
70 
39 
19 
9 
6 
6 
8 
( For D z = 150 m. 
0 
82 
109 
105 
73 
37 
26 
13 
6 
4 
4 
5 
the observed values fairly well. The previously determined values for D z fall mostly in 
this range also. This enables us to compute the values of vertical coefficient of mixing from 
formula (18). The above values of D z correspond to the values 188, 422, 750, and 1688 
g/cm/sec of A z , respectively. These are, of course, values consistent with the results de- 
rived from many other different sources. (Sverdrup, et al ., 1942.) 
Subsurface Circulation 
Figure 3b, c, d, e, and F show the horizontal distribution of streamlines in the level %D gi 
D z , l)/ 2 D z , 2 D z , and 3D Z below the sea surface, respectively. All give patterns similar 
to the sea surface circulation shown in Figure 3a. We have western currents and a boundary 
vortex attached to each gyre. The only difference noticed is a general subsidence of the 
motion as we go down into deeper layers. Still, we see that the intensity of motion is only 
reduced to as low as half that of the sea surface even in the layer 3D Z . Figure 4 shows the 
comparison of the current velocity profiles along the 33° N parallel at several levels to 
that on the surface of the sea assuming D z = 75 m. The maximum speeds are seen at 
about 55 kilometers off the western boundary. Although the Japanese Islands are not 
disposed parallel to a meridian, the above result agrees with the observed profiles of this 
mighty current quite satisfactorily. Another result of particular interest is that, at a 
distance greater than about 150 km., there is a flow to the south with much greater velocity 
than in upper layers. This counter current reaches a maximum speed of 20 to 30 cm/sec 
at about 200 km. off the western coast, despite the practically motionless upper layers. 
Figure 5 gives the comparison of the zonal distribution of E-W components along a merid- 
ian 24 degrees of longitude to the east off the western boundary. In this longitude it is 
expected that the influence of the western boundary nearly vanishes and the actual flow 
pattern of the Pacific circulation is disposed mostly as a zonal current system. The vel- 
ocities of the current in these diagrams were computed assuming D z = 75 meters. For 
computing the velocities when the value of D z is different, we have only to multiply these 
figures by 75/Xb, where D z is expressed in meters. If we assume, however, that the value 
D z = 75 m. is consistent, we have for the maximum surface velocities of the North Pacific 
Current, North Equatorial Current, Equatorial Counter Current, South Equatorial Cur- 
rent, and Antarctic Circumpolar Current 22, 19, 8, 23, and 23 cm/sec, respectively. They 
are reduced to 18, 16, 8, 18, and 18 cm/sec, respectively, at a level %D g and to 11, 9, 8, 
